Process of pretreating wood chips in the production of soda cellulose



Patented Dec. '1, 1926,

UNITED STATES PATENT 'OFFICE.

ERIK LUDVIG BI'NKAN. OF 153' UBS HOLH, SWEDEN.

PROCESS OF PBETBEATDS'G WOOD CHIPS IN THE PRODUCTION OFrSODA CELLULOSE-No Drawing. Application filed April 21, 1.20, Serial Roi 375,547, and inSweden Augult 18, 1918.

. of the raw material .with steam, but it has not been possible to pointout any particular advantages which will. compensate for the equallyhigh concentration as according loss of time caused by thepre-treatment, except in the production of sulphite cellulose.

The conditions of the manufacture of celluv lose, particularly in thesulphate process, are therefore at the present time such that 1t 1sconsidered to be better the drier the wood 18,

' and that a better economy of heat is attained by the waste liquorsbeing obtained in a more concentrated form. a

The present invention relates to a process of pre-treating the Woodchips or wood-like raw material,'such as bamboo in the production ofsoda cellulose which process has proved in practice to give aiiincreasedyield of cellulose, and which re-treatment may simultaneously be carrieout in. such manner that the waste liquors obtained have an to theprocesses of producing cellulose hitherto practised. The processconsists broadly in this that before the treatment with the chips aretreated witha hot-diluted waste liquor from a previous boiling at a.temperature lower than 100 (3., so that the percentage of water of thechips is increased, for instance up to 40 to per cent. When the portionof the pre-treatment liquid which has not been absorbed by the chips,has been wholly or partly removed, the ordinary boiling liquid isadmitted, when it is .to be observed that said liquid possesses suchhigh concentration that the desired concentration of the boiling liquidis obtained when the liquids have become mixed with one another. As aresult of this pre-treatment the chips become impregnated with a hotneutral liquid, owing whereto the action of the boiling liquidisaccelerated but is simultaneously modified to a very high extent so thatan essentially increased yield of cellulose is obtained. The yield ofcellulose may be increasedby 10 to 25 per cent as compared with thatobtained without the use of this pre-treatment. By this re-treatmentmore water is supplied to the c ips than according to the practice here-I it is desired shall be absorbe tofore followed, but the dilution ofthe boiling lye caused hereby may be compensated by using such greatquantity of waste liquor, when preparing the boiling lye, that thepercentage oforganic substances of the lye still mayrequire up to onehour m order'that V the desired result shall be attained. The desiredeffect of 'the pre-treatment. onl being obtamed if the liquid used ishot, t pretreatment may be applied with advantage also to so moist chipsthat they possess beforehand the percentage of water of approxto as thepercentage of water of the chips will not be imately 50 per cent abovereferred materially increased by treating moist chips with hot liquids.

The chips may be pre-treated in this manner either before they areadmitted into the boiler, or in the boiler. In the'latter case a savingof heat is gained, and the advanta e l is also attained that thequantity of-liquld absorbed by the 'chips'is easily measured measuringthe difference between the' am- 'tity of-liquid supplied to the boileran the quantity afterwards removed therefrom. It

is most advantageous to carry out the pretreatment in the boiler, asotherwise there will easily'be a loss of lye,

The practical application of the process 1s suite in aispecial receptace fromw 'ch it may be rapidly tapped or pum ed into the holler. Agreater uantity' of t e liquid than that 7 1y carried out in such mannerthat the pre-treatment li uor is ke tin hot state whlch may e absorbedby the chips ma bel let into the boiler, or only the (quantity w 'ch tThe admiss1on of the liquid into the boiler may suitably *begin when theboiler has been RPPIOXIr' mately half filled with chips and may beperformed so rapidly that all of the treatin liquid is supplied when theboiler is filled 'wlth chips. Afterwards. the liquid is re= tained inthe boiler during the refiuired riod of time during which it sho d prefably be kept in mot on so that the chips will become intimately mixedwith the liquid. This may be effected either by rotating the boiler orby causin the liquid to circulate. Meanwhile, the liquid may also beheated directly or indirectly, if considered suitable. The treatmenthaving been finished, theliquid which has not become absorbed by thechips, or which it is desired to remove from the boiler, is againdrained oil or pumped off into the same receptacle and may again be usedafter compensating for the material retained in the boiler. As regardsthe suitable quantity of treating liquid it may be stated as an examplethat in a rotary boiler having a capacity of 30 cu. m., 10 to 15 cu. m.treating liquid is used.

For heating the p're-treatment liquid the steam generated when thecontents of the boiler are blown over to the'difl'users, may suitably beused. The lye and fibres which are then possibly carried alon will stopin the pre-treatment liquid, so that no special arrangement forcollecting the same is necessary, but the receptacle for thepre-treatment liquid may form the required collecting devlce.

The process of pre-treatment above described, when carried out in theproper manner, is exceedingly simple and does not materially increasethe time of boiling, particularly when it is considered that the yieldof cellulose becomes considerably increased. In addition, the celluloseobtained is of a higher quality than that which it is possible to obtainif the wood chips are boiled directly without pre-treatment. As regardsthe result attained the present process has therefore a quite differenteffect from that of the old treatment of the wood chips with steam.

I claim; 1. The process of pre-treating wood chips in the production ofsoda cellulose, which consists in impregnating thewood chi s before thetreatment with the boiling iquidproper with hot diluted waste liquors ata temperature lower than 100 C. for the purpose of attaining a rapid butmodified action of the boiling liquid when afterwards supplied to thematerial. 1

2. The process of pre-treating wood chips in the production of sodacellulose, which consists in impregnating the wood chips before thetreatment with the boiling liquid proper with hot diluted waste liquorsat a temperature between 80 C. and'90'C. for the purpose of attaininga.rapid but modified action of the boiling liquid when afterwardssupplied to the material.

3. The process of producing soda cellulose,

which consists in impregnating wood chips with hot diluted waste liquorsat a temperature lower than 100 C., and afterwards treating suchimpregnated wood chips with a caustic soda lye.

4. The process of producing soda cellulose, which consists inimpregnating wood chips with hot diluted waste li uors at a temperaturebetween80 C. an 90 0., and afterwards treating such impregnated woodchips with a caustic soda lye.

ERIK LUDVIG RINMAN.

